Immunosuppressive Factor(s) Specific for L-Glutamic Acid⁵⁰-L-Tyrosine⁵⁰ (GT): I. Production, Characterization, and Lack of H-2 Restriction for Activity in Recipient Strain¹

The random synthetic copolymer of L-glutamic acid⁵⁰-L-tyrosine⁵⁰ (GT) fails to elicit a GT-specific antibody response in all inbred strains of mice tested. Preimmunization with GT specifically inhibits a GT-MBSA response in certain, H-2^d,k,s, but not other, H-2^a,b,q, nonresponder mice. This unresponsiveness is mediated by GT-specific suppressor T cells. Extracts prepared from lymphoid cells of GT-primed suppressor haplotype mice inhibit the development of primary GT-specific antibody responses to GT-MBSA in normal syngeneic mice. Nonsuppressor haplotype mice do not produce GT-specific suppressor factor. The GT-suppressive extract has affinity for antigen and a m.w. of less than 50,000 daltons, thus, resembling antigen-specific immunosuppressive factors already described. However, the GT-suppressive extract does not appear to have H-2 restrictions since it works across allogeneic barriers. Evidence is presented that two genes are required for factor-mediated suppression.